Air-conditioning technology for a domestic air conditioner progresses in both coolant and energy efficiency, and more comfortable life environment is required with the progress. Therefore, the air conditioner is made to have more functions not only for temperature but also for humidity control, ventilation, air flow control, and air cleaning. An improvement in energy efficiency is the most important issue also because of recent energy shortage. Also in hot and humid Asian countries, humidity control, in particular, dehumidification is considered to be important with improvement in standard of living. Performance of the dehumidification in an energy-saving manner can realize air conditioning with less environmental load. In dehumidification by cooling with coolant using a compressor that is a mainstream at present, a large quantity of energy is required to cool air so as to condensate vapor and to reheat the cooled air so as to regulate temperature. This increases power consumption, leading to an issue in magnitude of the environmental load.
In contrast, in a dehumidifier such as a desiccant air conditioner, a moisture absorber using an absorbent material absorbing vapor absorbs moisture in a room, and the dehumidifier heats the moisture and discharges the moisture to the outdoors. This dehumidification is therefore superior in energy saving performance to the coolant-type dehumidification. There are known absorbent materials made by impregnating a porous body such as porous ceramic or zeolite with a deliquescent substance made of bromide or chloride that contain sodium, lithium, calcium, or magnesium. The absorbent material (humidity controlling material), however, continues to absorb water and is finally saturated, and therefore needs to be subjected to regeneration treatment. The regeneration treatment for the absorbent material is performed by heating the absorbent material in order to discharge the absorbed water. Combination of the regeneration treatment (heat treatment) for the absorbent material and air cooling is inefficient.
As a method with less energy and at low cost alternative to the current air-conditioning method, a continuous dehumidification method using a vapor separator requiring no regeneration treatment is under discussion. An example of the structure of a humidity controller using the vapor separator is a structure in which a vapor separator made by filling a gap between two vapor permeable membranes using polyethylene or fluorine resin with a liquid absorbent such as a lithium chloride solution, is arranged between a space such as the interior of a room to be dehumidified and a space such as the exterior of the room. The vapor is sent and received between the air in the room and the liquid absorbent through the vapor permeable membranes. The vapor permeable membranes are, however, apt to break, and this method has difficulty in efficiently performing dehumidification because of low moving speed of vapor.